The following disclosure relates to a stabilizer provided on a suspension device of a vehicle and to a method of manufacturing the stabilizer.
Patent Document 1 (Japanese Patent Application Publication No. 63-312213) and Patent Document 2 (Japanese Patent Application Publication No. 63-46913) disclose stabilizers each formed of a pipe material and welded and fixed to a suspension arm at opposite end portions of the stabilizer. Not a thickening working but an expansion working is performed for the opposite end portions of the stabilizer disclosed in Patent Document 1. Description at lines 5-9 in the lower left column on page 2 in Patent Document 1 contains “since the section modulus z′ is increased by increase in diameter, enough strength is obtained for stabilizer mounting without thickening working, thereby achieving a stabilizer formed of a pipe without wasted materials”. Patent Document 2 discloses that end-portion-thickening cylinders are fitted on the pipe material at the opposite end portions of the stabilizer and caulked and merged with each other by a press fit of a cored bar into the pipe material. This process expands and thickens the opposite end portions of the stabilizer.
Patent Document 3 (Japanese Patent Application Publication No. 59-73136) discloses a stabilizer formed of a pipe material. One end portion of this stabilizer has an outside diameter less than that of an intermediate portion of the stabilizer. This end portion is serrated on its inner circumferential surface. The other end portion of this stabilizer has an outside diameter greater than that of the intermediate portion of the stabilizer. This end portion is serrated on its outer circumferential surface. An arm for torque transmission is mounted on the one end portion of the stabilizer using the serrations. The other end portion is mounted on a suspension arm using the serrations.